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Spheres with tangents and templates

Discussion in 'Woodturning Discussion Forum' started by John Kelsey, Feb 19, 2021.

  1. John Kelsey

    John Kelsey

    Joined:
    May 22, 2017
    Messages:
    42
    Location (City & State):
    Lancaster, PA
    For this week's Lancaster Woodturners coffee hour Angelo demonstrated sphere turning by the traditional method of tangents and templates, here's the video it's 8 mins:

    View: https://youtu.be/wtJ3ekHfo3E


    Woodturners Coffee Hour is open and free on Zoom every Thursday morning from 10 - 11 EST, message me if you'd like to visit.
     
    John Kelsey, Feb 19, 2021
    #1
  2. Dennis J Gooding

    Dennis J Gooding

    Joined:
    Apr 10, 2010
    Messages:
    651
    Location (City & State):
    Grants Pass Oregon
    An interesting video, but he does not explain how he comes by the hexagon pattern to do the measuring. One method is to measure or choose the diameter of the sphere and use a calculator to compute the facets of the hexagon. You may be interested in an alternative method of determining the measurements needed for spheres, spheroids and ovoids with no calculation required. I posted three articles in the Tutorial and Tips Forum on this subject. The are:

    Simple Aid for Turning Spheres without a Jig
    Simple Aid for Turning Spheres and Spheroids Without a Jig
    Simple Aid for Turning Ovoids
     
    Dennis J Gooding, Feb 21, 2021
    #2
  3. John Kelsey

    John Kelsey

    Joined:
    May 22, 2017
    Messages:
    42
    Location (City & State):
    Lancaster, PA
    Yah the dudes on the coffee hour shared several different ways to construct the octagon in the size you need. euclid octagon outside circle 1.jpg kai octagon.png davis octagon dwg.jpg
     
    John Kelsey, Feb 22, 2021
    #3
  4. hockenbery

    hockenbery AAW Advisor Staff Member

    Joined:
    Apr 27, 2004
    Messages:
    6,769
    Location (City & State):
    Lakeland, Florida
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    Angelos&myrons method is a good one and is well suited to get a sphere of an exact size.
    And a template should be constructed as accurately as possible.

    Your math examples are good.
    Here is another explanation
    D77529A6-0149-453B-80FE-B00BB6925629.jpeg

    the method I use is to turn between centers and rotate the ball. I cut my blanks DxDxD+1/2
    I get a sphere a little less than diameter D, the 1/2 added to the length takes the center points.

    after using .41 for years it occurred to me that I was an applied mathematician whose job is getting the wrong answers fast but knowing how wrong they are.

    so .4 works great for balls smaller than 6”.
    0F1B8649-7A60-4C42-BF1D-FF0C300EEFFC.png
    my method
    4090AA92-8551-4ECC-B491-057C08B300B6.png
    Also I find a using a ring check the sphere much better than a template.
    FCBC923A-28CB-46CA-A782-F528819291B3.png D71FAC98-3D5C-45F9-AB9C-131E51049A0C.png
     
    Last edited: Feb 22, 2021
    hockenbery, Feb 22, 2021
    #4
  5. Charles Chaloupka

    Charles Chaloupka

    Joined:
    Jan 4, 2020
    Messages:
    19
    Location (City & State):
    Niceville, Florida
    John can you send me info to join Thursday coffee hour. Thanks Chuck
     
    Charles Chaloupka, Feb 26, 2021 at 12:27 PM
    #5

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